Main Inclusion Criteria:

• The subject is a male or female, at least 18 years of age.
• The subject has a malignancy, is receiving opioid therapy for his or her underlying persistent cancer pain, and is tolerant to the opioid therapy.
• The subject typically has 2 to 6 episodes of target BTP per day that require treatment.
• The subject has a life expectancy of >3 months.
• The subject or his or her caregiver has easy, reliable access to a telephone.

Main Exclusion Criteria:

• The subject is a female who is pregnant or lactating.
• The subject has any respiratory or cardiac condition that, in the opinion of the investigator, may be clinically worsened by opioids.
• The subject has any allergy to the AD 923 product or excipients, namely: fentanyl, dehydrated alcohol, menthol, saccharin, and citrate buffer; or to the MSIR product excipients, namely: morphine sulphate, lactose (anhydrous), pregelatinized maize starch, povidone, purified water, magnesium stearate, talc, and tablet coatings.
• The subject has any neurological or psychiatric disease that, in the opinion of the investigator, would compromise data collection.
• The subject has uncontrolled or rapidly escalating pain.
• The subject has any significant laboratory test results that, in the opinion of the investigator, will compromise subject safety or the conduct of the study.
• The subject has plans to undergo chemotherapy, radiotherapy, or surgery during the treatment period. The exception is that subjects may continue chemotherapy over the study period, provided it is not expected to alter the pain state or response to pain medication.